UI Performance Issue

[ds5678]

Steps to reproduce

1. Open ILSpy
2. View a class
3. Click on another class in the tree view

On ILSpy 9.1, there is multiple-second lag in step 3.

Details

• Product in use: ILSpy
• Version in use: release 9.0 and 9.1
• Any other relevant information to the issue, or your interest in contributing a fix.
  • I thought it might have been caused by a592169, but I reverted that locally, and the lag was still present.
  • I initially posted about this in UI Performance Issue? #3485 before I did any investigation.
  • 3b83029 is currently the oldest commit with an unexpired actions run. The lag is present on that commit.

[siegfriedpammer]

I cannot reproduce this.

[ds5678]

Might need a bigger assembly to be noticeable. Try this one.

https://www.nuget.org/packages/AssetRipper.SourceGenerated

[siegfriedpammer]

Is there a specific type I should look at?

[ds5678]

For me, there does not seem to be a difference. Any type is sufficient.

[siegfriedpammer]

There is no perceivable delay on my machine.

[ds5678]

2025-06-01.11-29-39.mp4

I'm going to bisect the changes.

[ds5678]

I finished my bisection.

https://github.com/icsharpcode/ILSpy/actions/workflows/build-ilspy.yml?query=branch%3Amaster

51522c4 is the last actions run without the problem.

96caa4e is the first actions run with the problem.

[siegfriedpammer]

So the problem seems to be 128f83d?

[ds5678]

Yes, I think so.

[siegfriedpammer]

Can you try to profile it? I don't see anything particularly expensive in that change...

[ds5678]

The vast majority of time is spent in ICSharpCode.ILSpy.Options.DecompilerSettings::Clone().

[ds5678]

I made a pull request, which kind of solves the problem, but not really. I made cloning the settings enormously faster, but I did nothing to address why it was being cloned so much more than before.

With my changes, I don't experience a lag anymore in the UI.